Silas t



UNITED STATES- PATIJNT -Orrica siLAs T. Jackson, oFsHnnoYGAN rants, WISCONSIN.

sEfLF-CENTERING .CHUCKQ- Specification forming part oi' ,Leiters lzitent No. 50,593, dated October 24, 1.865.

To all otom it may concern:

vBe it known that I, SILAs T. JACKSON, ot'

-Sheboygan Falls, in the county of Sheboygan and State of Wisconsin, have invented a new and useful Improvement in Self-Centering Chucks; and l do hereby declare the followa. vertical section on the linect 1.-. Fig. 5 shows the jaws detached.

My invention belongs to that class of chucks which are constructed with screws l'or the purpose of operating the jaws; and its nature consists in such a construction as shall enable me with adouble screw, the pitch of one being just half the pitch ofthe other, to operate the jaws simultaneously` inopposite directions, so that they will approach or recede from the center at equal speeds, thercbyforming` a self-cen# tering mechanism of' very simple and inexpensive yet effective form.

That others may understand its construction and operation, I will particularly describe it.

A, Fig. 5, is the lower, and B is the'upper, jaw. The lower jaw, A, is securely attached to the guide-rods U C, and these latter are inserted through proper holes in the jaw B, so that the latter jaw may have afree motion back and forth upon said rods. The yoke D vthen connects the upper ends of the rods Gv C, and it is by means ot" this `yoke that the rods are drawn back' and forth and communicate motion to the jaw A.

At the center of the yoke D a nut is formed for the screw E, which, passing*throughsaid nut, rests at its lower end upon the upper side of tbe upper jaw, B, so thatitis evident, if the screw E be run through the nut in the yoke D, it will cause'the jaw B to descend upon the jaw A, orl they will be forcibly drawn together, claspin g and holdingjirmly whatever happens to be inclosed between them.

Springs or equivalent devices should beA placed between the jaws, so that when the pressure of the screw is relaxed theywill move il il away .from each Aother automatically. This function -ot' the parts already described is too coinnion and well known to require further setting forth here.

lt is now required lha-t l should describe the peculiar arrangement by which the jaws A and B should be retained always equidistant from a. lcertain tixcd point which is coincident with the axis ofthe mandrel to which the chuck is 'to be attached.l

In order to' accomplish the objects l'or which a chuck is designed, it is, ofcourse, necessary thatthe working parts should be attached permanently to some rigid body, which, in turn, may be attached to the lathe or other engine. A suitable shell onframe-work is therefore provided having' the requisite means ot' attach'- ment to the turning-engine. This shell or frame is also provided with proper hearings for the guide-rods C C,soarra 1 nged that as thc rods lslip in their bearings the center points' or notches, F, ofthejaws will move always in aline passing' over the axial point before spoken ot'.

This is not difficult of execution. It now be-v comes necessary to cause the jaws to recede from or to approach this axial point through the operation of turning the single screw E. I therefore reduce somewhat the size ot' the bolt upon which the threads ot' the screw E are formed, and upon that reduced portion l form the threads of the screw c. The pitches of these twoscrews should be exactly as one to two, the pitch of E beingjust double the pitch ot c. 'A nut, G, fitted to the screw c,'is made, and .is firmly and rigidly attached to the shell or frame o't the 'chuck, and when the parts are in place, the jaws firmly screwed together and exactly central to the axial point before mentioned, the lower end of the rod upon which these two screws are formed should bear upon the upper side of the jaw,v B, and the nut Gr should be up very near to the shoulder formed at the junction 'ot' the two screws, (see Figs, 1 and 4,) and there should be as much space below it for the jaw B to ascend as there is -above it for the yoke D and jaw A to descend.

It will now be perceived that if the Iscrew E be turned backward the screwc will rise through the nut G andthe jaw B will follow it. It', now, the screw E was in `pitch exactly equal to the screw c, the yoke 1) and jaw A would remain stetionztr out ne pitch ot' E is .inst double the pitch of' c, and therefore,`

'yoke D has traversed on the screw E twice that distance, and has heen obliged to descend irhile its screw rises. Itis therefore apparent that 'the movement of the yoke D and jaw A upon its screw E isjnst double the movement et' thejztw B5 lint it is also apparent thatjust one-heit' o' seid movement ot' the yoke l) and jim ji. absorbed oy the lateral movement ot' the Screw Eil itself, so that the actual descent of the jow A is exactly equal to the ascent of the v: ii. Ziie reversion ot' the movement of the ,W operates the i:tws in the opposite dirrcticn, lint does not' change the character ot' their increment. The soresr E may in practice be turned by n, key, crunk, or any other device suitable or convenient in View ot' the special construction or adaptation ot' my iinplenient.

'the ivrroportions of the relative parts of my invention nre' not represented in the dro-wings with accuracy, though I think they clearly repiesent the peculiarities ot' its construction and the principle upon which it acts. The details et' its construction may he grently -oiried to adapt it to the Various positions or kinds of work with which it is to be used, Without altering the principle npon which it acts.

Among theadvantnges pertaining to this airrztngenicnt I may mention clieapness and simplicity ofconstrnction, facility ot'use, and adaptation to speciztl purposes, tlictccnracyof menut'acture w ithout the use ofthe costly machinery sometimes necessary, nndlast, thcnghnot leest, the open center, not possessed, lbelieve, by any ctherscltcentering screw-chuck, thus allowing; smell work, es in turninglthe end of @slender .rod to be inserted through the chuck and holiow mandrel ot' the inthe, so es to grasp the work neer the point to be operated upon. The jews are constructed so es to fit or grasp objects o't various sizes.

Hering described my invention, wlmtlclztim as new, and desire to sccnre by Letters Petent, is y y n combination with the movable jews ot' chuck, e ditterential screw', operating; snostnntally es described, so as to i'orm a seltfcentcring chuck, as set forth.

' SIL-AS .l. AUKSUN.

Nitnesses JAMES HANFORD, QATHARINE M. HANFORD. 

